1. Field of the Invention
The present invention relates to a semiconductor device having a circuit composed of thin film transistors (hereinafter referred to as TFTs) transferred by bonding a peeled layer (to be peeled) to a base member and a manufacturing method thereof. More particularly, the present invention relates to an electro-optical device which is represented by a liquid crystal module, a light emitting device which is represented by an EL module, and electronic equipment on which such a device is mounted as a part.
Note that a semiconductor device in this specification indicates general devices functioning by utilizing semiconductor characteristics, and an electro-optical device, a light emitting device, a semiconductor circuit, and electronic equipment are all semiconductor devices.
2. Description of the Related Art
In recent years, a technique of constructing a thin film transistor (TFT) using a semiconductor thin film (about several to several hundred nm in thickness) formed on a substrate having an insulating surface has been noted. The thin film transistor is widely applied to an electronic device such as an IC or an electro-optical device. In particular, the development of the thin film transistor as a switching element of an image display device is urgently necessary.
Various applications utilizing such an image display device are expected, and particularly its utilization in a portable device is noted. Currently, a glass substrate or a quartz substrate is used for forming the TFT in many cases. However, there is a defect that the above substrate is easy to crack and heavy. In addition, in the case of mass production, it is difficult and thus not suitable to use a large size glass substrate and a large size quartz substrate. Thus, it is attempted to form a TFT element on a flexible substrate, typically, a flexible plastic film.
However, the plastic film has a low heat resistance, so that it is necessary to reduce a maximum temperature of a process. As a result, under the current circumstances, a TFT having a preferable electrical characteristic cannot be formed on the plastic film as compared with the case where the glass substrate is used. Therefore, a liquid crystal display device and a light emitting element for which the plastic film is used and which each have a high performance are not realized.